When I started shooting USPSA, squad-mates would pick up your brass and return it to you, but today, picking brass is generally done in whatever downtime there may be between stages, or after the match. When a lot of people were shooting .38 Super and Super Comp, they wanted to get their own brass back, but now that so many people are shooting relatively cheap and plentiful 9mm, lots of people seem to be happy to leave it on the ground.